Forest and Rangeland Birds of the United States

Natural History and Habitat Use

Greater Scaup -- Aythya marila

RANGE: Breeds from western Alaska to southern Keewatin, around Hudson and
James Bays, and northern Quebec; casually or irregularly south to southeastern
Alaska, northwestern British Columbia, central Manitoba, and southeastern Michigan.
Winters along the Pacific Coast from the Aleutians and southeastern Alaska south
to Baja California, in the eastern Great Lakes, from the Ohio and lower Mississippi
Valleys south to the Gulf Coast, and on the Atlantic Coast from Newfoundland south
to Florida.

STATUS: Locally common.

HABITAT: Inhabits lakes, ponds, and marshes from forested tundra to
richly vegetated low tundra. During the breeding season, drakes rest along shorelines
or on shoals, while in late fall and winter, both sexes form large rafts in
open water, even in the open ocean well beyond the breakers. Winters on brackish
and saltwater bays and estuaries, less commonly on large inland waters.

SPECIAL HABITAT REQUIREMENTS: Scattered wetlands in forested to open
tundra.

NEST: Nests on the ground in a slightly elevated spot, in grasses on
the tundra, usually near the shores of lakes or ponds, but up to 3,000 feet
from water. Sometimes nests on islands, in marshes, or above or in water among
rushes or wild rice.

FOOD: An expert diver; dives to depths of at least 20 feet, remaining
underwater seeking food for up to a minute. A saltwater bird most of the year;
prefers to feed in shoals with water less than 20 feet deep or in shellfish
beds, also in freshwater lakes and ponds. Consumes a diet that is about half
vegetative and half animal, including snails, aquatic insects, tadpoles, small
fishes, and seeds in summer. During winter, also eats mollusks, crabs, barnacles,
and other crustaceans. Also feeds on muskgrass, sea lettuce, eelgrass, wild
celery, and widgeon grass.